Automobile interior parts such as installment panel and door panel are typically manufactured by injection molding. In manufacturing such parts, reduction in manufacturing cost without deterioration in favorable appearance has been demanded.
However, when injection molding is conducted with use of a die having a plurality of gates for injecting a melt resin, weld (also known as weld line or weld mark) is generated at an area where a plurality of resin flows are merged together, which leads to deterioration of favorable appearance. The same problem also arises when a resin flow is divided and subsequently merged together with use of a die for providing molded products having openings.
While products with weld have been conventionally subjected to post-process such as coating and touch-up in order to keep a predetermined level of appearance quality, such post-process unfavorably increases manufacturing cost.
Thus, several proposals have been made on an injection-molding die and an injection-molding method capable of suppressing generation of weld and providing molded products for which no post-processing is required. According to one exemplary proposal, a die is provided with a heat insulation structure, so that resin flows are merged together at high temperature for prevention of generation of weld (patent document 1).
Patent Document 1: JP-A-2000-334743